ET II General - Set 1
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1.
According to Lenz's law, the eddy currents induced in a test part produce a magnetic field that:
2.
In 1824 Arago showed that a rotating copper disc exerts a force on a nearby magnet. This was early evidence of:
3.
Which pioneer used an induction balance in 1879 to tell different metals apart, an early form of eddy current sorting?
4.
Faraday's law states that the voltage induced in a coil is proportional to:
5.
Using δ(mm) = 50·√(ρ/(f·μr)), what is the standard depth in 304 stainless steel (ρ ≈ 72 µΩ·cm, μr = 1) at 100 kHz?
6.
Eddy current density at a depth of two standard depths is approximately what percentage of the surface density?
7.
If the test frequency is raised by a factor of 100 with everything else unchanged, the standard depth:
8.
At a depth of two standard depths, eddy currents lag the surface currents in phase by approximately:
9.
A metal has a resistivity of 3.45 µΩ·cm. Its conductivity is closest to:
10.
Which of the following materials is diamagnetic, with a relative permeability slightly below 1?
11.
Annealed 304 stainless steel is normally non-magnetic. Heavy cold work or welding can:
12.
When a ferromagnetic steel is heated above its Curie temperature, it:
13.
When a surface coil is placed on a non-magnetic conductor, the coil's resistive component typically ___ and its inductive reactance typically ___.
14.
A coil has an inductance of 80 µH. What is its inductive reactance at 100 kHz?
17.
On the normalized impedance plane, the resistance and reactance values are both divided by:
18.
On a normalized impedance plane, an unsaturated ferromagnetic steel part usually places the operating point:
19.
With the same probe and part, raising the test frequency moves the operating point on the non-magnetic locus:
20.
Using fg = 5066/(σ·μr·d²), a brass rod with σ = 16 MS/m and d = 1.0 cm has fg ≈ 317 Hz. Which test frequency gives f/fg = 10?
21.
If the diameter of a bar doubles while its material stays the same, its characteristic frequency fg:
22.
Compared with crack detection in bar, conductivity sorting with an encircling coil generally uses:
23.
A 15.0 mm diameter bobbin probe is used in a tube with an inside diameter of 17.0 mm. What is the fill factor?
24.
Why does a poor fill factor reduce the quality of an encircling or inside-coil test?
25.
How does a surface probe's signal change as liftoff increases from zero?
26.
A crack signal measures 1.2 V peak-to-peak and the background noise 0.3 V. The signal-to-noise ratio is:
27.
An operator doubles the instrument gain to make a weak flaw signal easier to see. The signal-to-noise ratio:
28.
Scanning a weld near a running welding set, the display shows fast, spiky hash superimposed on every signal. Which filter setting is aimed at this?
30.
Why is the bridge balanced (nulled) on defect-free material before testing?
31.
A differential bobbin probe passing a small hole typically produces what pattern on the impedance-plane display?
32.
In the reflection (driver-pickup) mode of operation:
33.
Compared with a differential coil arrangement, an absolute coil is better at responding to:
34.
Compared with a large pancake coil, a small pencil probe generally offers:
35.
After a steel part has been tested with DC magnetic saturation, what may be needed before it moves on to later processes?
36.
As described in CP-105, calibration of an eddy current instrument means:
37.
A technician can read Jaeger J2 letters only when the chart is held 8 in (20 cm) away. Under SNT-TC-1A, this:
38.
A candidate scores General 75%, Specific 72% and Practical 90%. Under SNT-TC-1A recommended grading, the candidate:
39.
Under SNT-TC-1A 2024, the recommended minimum experience for ECT Level I is:
40.
SNT-TC-1A lists ACFM, ECT and RFT as techniques within which NDT method?